Power failure is a major problem in microprocessor-based systems. A power outage such as drop-out, brown-out, or blackout, may cause momentary or long-term loss of power and may occur unpredictably. When the power to the system is turned off, either accidentally or due to a power outage, critical information contained in volatile memory may be lost.
Existing techniques to protect data during a power failure have a number of drawbacks. Typical techniques employ battery backup memory modules. Data are stored in these memory backup modules and battery is used to provide power to these memory modules during loss of power. A major disadvantage of this technique is the cost of the battery. In addition, complex circuitries are used to support the battery-operated mode. Furthermore, battery life may be degraded for extended use and replacement of batteries may be expensive.